Storage and Food Preservation lesson for class VIII
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Storage and Preservation of Food
Transcript
1. Storage and Preservation of Food
2. Some micro organisms spoil the food materialThe food
material gets spoiled if not stored properly
3. Eating such spoiled food is dangerous to health it may
result in vomiting, diarrhea and even deathThis is known as Food
poisoning.
4. Reasons for storing food properly are-Make them available
through out the year.
5. Reasons for storing food properly are-Make it easy for the
distribution to distant places in the country
6. Reasons for storing food properly are-Reduce the wastage of
food material.
7. We will learn how to prevent spoiling of food materials by
Micro organisms pests and rats. Bacteria and Fungi are the micro
organisms which spoil both cooked and un cooked food materials.
Souring of milk, curd and buttermilk is due to Bacteria. Bacteria
grow rapidly if the food is stored between 200C and 400C. Some
bacteria act on the food material and degrade them to simple
compounds. Fats to fatty acids, Proteins to amino acids and Sugars
to CO2 and H20
8. We will learn how to prevent spoiling of food materials by
Micro organisms pests and rats.Some bacteria produce toxic
substances which contaminate the food( Clostridium grows on fish)
.
9. Fungi grow in warm, dark and damp conditions.Fungi grow
rapidly if the food is stored between 200C and 300C.Growth of Fungi
on food can be detected by the white glistening filaments with grey
or black or yellow dust like spores on the food material.
10. Aflatoxin produced by the fungus on improperly stored
ground nuts is poisonous and damage liver.
11. Sun drying:Micro organisms need moisture to grow.Moisture
can be removed from food by drying or adding sugar or salt to
it.Vegetables and fruits are washed, peeled and dried in the
sunlight .During the drying process water content of the food
material is reduced to 5% from 60%-70%.
12. Sun drying:AdvantagesLeast expensive and very
effective.
13. Sun drying:DisadvantagesPossible when there is a bright sun
(Seasonal)As food is exposed to dirt and insects, there is a risk
of contamination and spoilage.
14. Mechanical Drying:Dehydrators and spray dryers are the
devices, which control temperature and humidity, used for drying
food materials in industries.
15. Mechanical Drying:Foods spoil if they are dried at high
temperatures are dried using spray drying under sterile conditions.
(Milk Powder making)
16. Smoking:Foods dried by exposing them to smoke from burning
wood. Heat from the smoke helps to remove moisture from the
food.Smoke gives characteristic flavour to the food.Fish and meat
are preserved in this method
17. Salting:Food material is cut in to pieces and large
quantity of salt is added to remove moisture.External moisture is
removed by drying.
18. Salting: In some cases further processed to make pickles.
Tamarind, Amla, Lemon, raw Mango, Fish etc. are preserved in this
process. Pickle
19. Freeze Drying: Microbial growth is retarded when food is
stored at low temperature.
20. Freeze Drying: The lower the temperature, the higher the
retardation.
21. Freeze Drying:Food is stored temporarily in cellars with
temperature is about 150C.
22. Freeze Drying: At this temperature decomposition and the
growth of micro organisms is slowed down considerably.
23. Use of high temperatures:Application of heat leads to the
destruction of micro organisms present in food. Temperature and
duration depends on the type of food and the type of micro
organisms to kill. Boiling of milk is an example for this
process.
24. Pasteurisation:Milk is preserved in this process, which is
devised by Louis Pasteur.Milk is heated to 720C for 15 seconds to
kill harmful bacteria.Then quickly cooled to 100C.Transferred to
sterile bottles or polythene bags, sealed and stored at 100C till
distribution.
25. Canning:Fresh food is cooked very quickly and transferred
to a sterile container.Salt or Sugar solution is added .Air is
removed and sealed tightly.Once again heated to kill any microbes
entered by chance.Vegetables, meat and fish are stored in this
process.
26. Prevention of spoiling of food by pests: Worms, insects and
rats damage food materials. Reduce their nutrient content. Make
them unfit for human consumption. Some times transfer disease
causing bacteria to food material. Fruit fly
27. Estimated damage to food grains by rats is 30%-40% of total
production.
28. Insect pests are controlled by: A)Spraying. The grain
storage area is sprayed with insecticide like DDT, Malathion etc.
before storing the food material. This will kill insects in the
storage.
29. B)Fumigation.Pests present in the grains and storage area
are killed either by ethylene bromide or aluminum phosphide.These
chemicals are kept in storage area react with moisture and form a
poisonous gas.
30. Rat control:A) Mechanical method.Rat traps are used to
catch the rats.This is not very effective method
31. B) Chemical method.Rats are killed by chemicals like Zinc
Phosphide and varafin which act as poison to rats.A bait of small
balls is prepared with mixture of wheat flour, oil and sugar is
kept near the storage for 7-10 days.Then poisoned bait is placed to
kill the rats.Dead rats must be removed immediately.